In a Long Term Evolution (LTE) network architecture, multiple mobility management entities (MMEs) in an MME pool simultaneously serve a same wireless area, where each MME in the MME pool is interconnected with all base stations in the MME pool, and the MMEs in the MME pool share resources, and share service load.
When an MME in the MME pool becomes faulty, if user equipment (UE) attached to the faulty MME actively initiates a service request, a base station serving the UE sends, using a preset policy, for example, a load balancing principle, the service request of the UE to another MME that works normally in the MME pool. The MME that works normally rejects the service request of the UE, and the UE needs to re-attach to the MME that works normally in order to implement service recovery, thereby implementing redundancy among MMEs in the MME pool.
However, a redundancy effect of the solution provided in other approaches is relatively poor, for example, when a UE needs to initiate a Voice over LTE (VoLTE) mobile originated service, and an MME to which the UE is attached becomes faulty, a base station that provides a service for the UE sends a VoLTE mobile originated service request message of the UE to a new MME in the MME pool, but the new MME rejects the VoLTE mobile originated service request of the UE. The UE of which the service request is rejected attaches to the new MME by re-initiating an attach procedure, and re-initiates a VoLTE mobile originated service, and then the new MME provides a service for the VoLTE mobile originated service of the UE. This causes that the VoLTE mobile originated service of the UE cannot succeed at a time. In addition, after an MME becomes faulty, service requests initiated by all UEs that are attached to the faulty MME are rejected by a network side, which triggers new attach procedures of these UEs, and attach procedures generated by a large quantity of users in a relatively short time bring great signaling impact on other network elements, such as a home subscriber server (HSS), in an LTE network, causing HSS congestion. The HSS is a critical node in the entire network, and HSS congestion causes a failure in accessing the network by a user, or a sharp decrease in a VoLTE call success rate.